Manufacture of motor fuel



L. C. KEMP MANUFACTURE 0F MOTOR FUEL April 15, 1941.`

Filed Aug. l5, 1959 Alli' ZOEIE m Patented Apr. 15, 1941 MANUFACTURE OF MOTOR FUEL Lebbeus C. Kemp, Port rthur, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application August 15, 1939, serial No. 290472 2 Claims.

This invention relates to the conversion of lower molecular weight hydrocarbons to higher molecular Weight hydrocarbons and has to do particularly with a process for the simultaneous production of a relatively high octane motor fuel and a high octane aviation gasoline.

Broadly, the invention contemplates a process for the conversion of natural gasoline hydrocarbons to Yhigh octane motor fuel hydrocarbons, which involves separating a fraction comprising butanes from natural gasoline and subjecting the higher boiling constituents of the gasoline to thermal conversion for the production of olefin hydrocarbons. The olefin hydrocarbons comprising C3 and C4 hydrocarbons are removed from the products of conversion, leaving a fraction comprising hydrocarbons suitable as motor fuel of relatively high anti-knock value. The olen hydrocarbons are subjected to alkylationwith isobutane derived from the butane fraction of the natural gasoline to produce aviation gasoline of high anti-knock value.

The butane fraction of natural gasoline comprises both normal butane and isobutane and, therefore, the invention contemplates subjecting the normal butane to isomerization for the production of isobutane, which is subsequently a1- kylated with the olefin hydrocarbons produced in the thermal conversion step.

In order to describe the invention more fully reference will now be made to the accompanying drawing comprising a flow diagram illustrating a general method of flow for the process of this invention.

Referring to the'drawing, natural gasoline is conducted from a source, not shown, through a pipe I communicating with a fractionating unit 2. The natural gasoline may be comparatively free from propane and lighter hydrocarbons and may contain around 2li-40% of normal and iso butanes.

This gasoline is subjected to fractionation so as to separate therefrom separate fractions respectively rich in normal butane and isobutane. Inv the event that the feed gasoline contains propane and lighter hydrocarbons provision may be made for removing all or a portion of these lighter hydrocarbons as a separate fraction in the fractionation unit 2.

The fraction comprising hydrocarbons of higher molecular weight than butane is removed from the lower portion of the fractionation unit 2 through a pipe 3 leading to a reforming unit; 4, which may be of either the thermal or catalytic type. In the unit 4 the hydrocarbons are subjected to cracking temperatures which may range from around 950 to 1050 F., for example, and while under pressure which may range from around 50 to 1000 pounds per square inch gauge. The conditions of temperature and pressure, as Well as duration of temperature treatment in the unit 4, are regulated so as to realize the desired degree of conversion of saturated hydrocarbons to olefin hydrocarbons and particularly Ca and C4 olens.-

Additional saturated hydrocarbon feed may be drawn from an extraneous source, if necessary, through a pipe 20 communicating with the inlet to the reforming unit 4.

- The products of conversion are passed from the unit 4 through a pipe 5 to a fractionation unit 6. The products are there subjected to fractionation to remove gaseous constituents, including fixed gases, propane and the like, which are drawn off through a pipe 1. If desired, the low-boiling hydrocarbons drawn off at; this point may be subjected to further treatment, such as catalytic,

polymerization for the production of polymer gasoline.

A further fraction is produced from the unit 6 comprising Cs and C4 hydrocarbons, a large proportion of which are olefin hydrocarbons. This fraction is drawn off through a pipe 8 leading -to an alkylation unit, 9 to which reference will be made below.

The high boiling constituents of the products of conversion from the unit 4 may be Withdrawn from the fractionation unit 6 through a pipe l0 and will comprise gasoline hydrocarbons of rela- `tively high anti-knock value; forv example, having an octane value of around -85 (C. F. R. M.). The fractionation is advantageously controlled so as to produce a fraction having a boiling point not in excess of around 395 or 400 F. If, as a result of the reforming step, higher boiling hy drocarbons are present, these may be removed as a separate fraction through a pipe l l.

The isobutane fraction produced from the fractionation unit 2 is conducted through a pipe I2 to the alkylation unit 9 already referred to and to which the olefin hydrocarbons from the pipe 8 are introduced. During alkylation these hydrocarbons are subjected to contact with an alkylation catalyst such as concentrated sulfuric acid or a liquid prepared by completely saturating Water at about room temperature with boron trifluoride.

'I'he alkylation unit may comprise a single reaction stage or a plurality of such stages such as described, for example, in my pending applireacting liquids inthe liquid phase;

cation, Serial No. 238,715, relating to a. method for manufacture of anti-knock hydrocarbons. It is to be understood, however, that the specific manner in which the reaction is effected, as vvell as the operating conditions employed, may be varied so as to produce the results particularly desired.

Where sulfuric acid is the alkylation catalyst it is desirable to use an acid having a, concentration of around 90100% and, preferably, about 9498% H2804. tion reaction may range from around -120 F., but advantageously is about 60-90" F'.

Sufficient pressure is employed to maintain the The ratio of isobutane to olei'ins in the mixture entering the alkylation unit is at least about 1:1 and preferably about 3:1 to 5:1. The ratio of acid to total' hydrocarbons in the reactor may be around 0.5 to 2.0 parts by volume of acid to one hydrocarbon. v

The products of the alkylation reaction, after having been neutralized, are conducted through -a pipe I3 to a fractionation unit III. This fractionation is for the purpose of removing propane and lighter constituents which may be present, as well as for the removal of unreacted isobutane and normal butane. The fractionation may be regulated so as to produce a gasoline fraction suitable as aviation motor fuel as, for example, having an end boiling point of around 311 F. with an octane rating of around 90 or above..

The unreacted isobutane is recycled through a pipe I5 to the alkylation unit 9. The normal butane fraction produced from the unit I4 is conducted through pipe I6 communicating with a pipe I1 through which the normal butane fraction produced from the fractionationl unit 2 passes to an isomerization unit I8.

In the unit I8 the normal butane is subjected to contact with an isomerization catalyst, such as anhydrous aluminum chloride, in the presence of a small amount of hydrogen halide, so as to convert the butane'to isobutane. For example, the reaction may be carried out in the vapor phase at temperatures of about 190-220 and under pressures of about 175-250 pounds per square inch. The off-gases from this reaction may be either recycled in toto, with washing to remove `hydrogen halide, or subjected to fractionation.

The isobutane so produced is Withdrawn and conducted through a pipe I9 communicating with the inlet to the alkylation unit 9, previously referred to.

While certain conditions and other details of operation have been mentioned, it is contemplated that these may be varied as desired, depending upon the character of the gasoline hydrocarbons undergoing treatment, as Well as upon the particular nature of the final products desired.

Obviously many modications-and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a process for-the conversion of natura gasoline hydrocarbons to high octane motor fuel hydrocarbons the steps which comprise fractionating natural gasoline to -separate therefrom fractions respectively rich in normal butane and isobutane and to produce a fraction comprising mainly hydrocarbons of higher molecular weight than butane, subjecting the normal butane fraction to isomerization to produce isobutane, subjecting the fraction comprising hydrocarbons o f higher molecular Weight than butane to thermal conversion to form olefin hydrocarbons including normally gaseous olefins, fractionating the products of conversion to separate therefrom a.

fraction comprising C3 and C4 hydrocarbons, including olens, and a high boiling fraction comprising motor fuel hydrocarbons of relatively high octane rating, subjecting said C3 and C4 fraction to alkylation with said isobutane, and subjecting the products of alkylation to fractionation to separate therefrom a fraction comprising hydrocarbons suitable as aviation motor fuel of high octane value.

2.'In a process for the conversion of natural gasoline hydrocarbons to high octane motor fuel hydrocarbons, the steps which comprise fractionating natural gasoline to separate therefrom fractions respectively rich in normal butane and isobutane and to produce a fraction comprising mainly hydrocarbons of higher molecular weight than butane, subjecting the normal butane fraction to isomerization to produce isobutane, subjecting the fraction comprising hydrocarbons of higher molecular weight than butane to thermal conversion to form olen hydrocarbons, including normally gaseous olefins, subjecting the products of conversion to fractionation, separating therefrom a normally gaseous fraction comprising C3 and C4 olens, separating another fraction comprising motor fuel of relatively high anti-knock value, subjecting the C3 and C4 hydrocarbon fraction to alkylation with said isobutane derived from the lower boiling portion of the feed, subjecting the products of alkylation to fractionation, separately removing isobutane and normal butane from the alkylated hydrocarbons, forming from the alkylatedA hydrocarbons another fraction comprising aviation motor fuel of high octane value, recycling at least a. portion of the isobutane removed from the alkylated hydrocarbons to the alkylation operation and recycling at least a portion of the normal -butane separatedl from the alkylated hydrocarbons to the isomerization operation.

LEBBEUS C. KEMP. 

